"There was a time when intelligent people used literature to think," wrote Amy Bellette in a letter in Philip Roth's 2007 novel Exit Ghost. "That time is coming to an end." How enthusiastically Roth himself endorsed this position was not entirely unambiguous – Bellette, an elderly woman whose mental processes had been ravaged by a brain tumour, might in any case have been acting as the mouthpiece of a long-dead writer – but he put the words out there, folding them into a larger argument about the ethics and intellectual purpose of literary biography and the perils of mistaking gossip for criticism. There was, undoubtedly, an element of challenge – an instruction to readers to think, to be "alone with the books, to make of them what they would on their own". Given that Exit Ghost, alongside Everyman and now The Humbling, is part of a suite of late novels that derive their momentum and urgency from the prospect of decay and the ebbing of personal power, it is no surprise that Roth should make a case for reading with a minimum of background chatter. He has something to say, and he wishes to say it.

What, then, to make of a novella that chooses as its focus the bewildered losses of an ageing actor, a man who, on discovering that he has become "a self-travesty grounded in nothing", develops a fear of the words "thin air", as spoken by Prospero, sensing in them "an obscure indictment"? Or who, terrorised by feelings of inauthenticity and fraudulence, quits the stage merely to launch himself into a sexual and romantic liaison so comprehensively doomed that his appetite for it can only seem like self-slaughter? If this is literature that we can use to make us think, then what direction does its creator want us to head off in?

Simon Axler, "the last of the best of the classical American stage actors", a 65-year-old with Falstaff and Vanya and Peer Gynt safely under his belt, has lost it. Not so much humbled as utterly humiliated, he has crashed – ostentatiously, dramatically – in a demanding double bill of The Tempest and Macbeth. His subsequent nervous collapse is punctuated by the departure of his wife, a former ballerina whose career-ending injury has left her more pathetic than erotic, and a brief stay in a psychiatric hospital. There, Simon's crisis is given a little more perspective, first by the disturbingly banal conversations of a group of failed would-be suicides, and then by the more cogent account of a middle-aged female patient who one afternoon discovered her husband abusing his eight-year-old stepdaughter. She, too, has been undone by an inability to act; unlike Simon, her paralysis has implications and consequences that will never cease. Simon, perhaps taking the hint, decides that the only sensible thing for him to do is to shut up shop altogether. Back at his remote farmhouse in upstate New York, his most meaningful interaction with another living creature comes when he witnesses how little an ailing possum needs to furnish his lair: "Six sticks. So that's how it's done, Axler thought. I've got too much. All you need are six."

Thus far, we are more or less with Roth, unpicking the similarities and contrasts he sketches – and even at its most intricate and resonant, this narrative is only ever a sketch – between different kinds of action, different varieties of protagonist and audience; and reflecting on how much we are allowed to read into such a strikingly unadorned presentation of an artist whose confidence – significantly described as his ability to listen – suddenly deserts him, and leaves him at the mercy of "the omnipotence of caprice". How, though, to stay with him through the novella's next act?

Retreats, in fiction if not in fact, are made to be penetrated, so it is little surprise when a figure from Axler's past turns up out of the blue, nor even that she is the daughter of old acting friends. That she is a 40-year-old lesbian who, abandoned by a lover whose next port of call is a gender reassignment clinic, has decided to make a leap into heterosexuality is more startling. But when we find that Pegeen – named after a character in The Playboy of the Western World – has deliberately selected Simon for her experiment in sexuality, despite knowing next to nothing of his circumstances, or him, their affair begins to look like a horribly forced device. As it unfolds, each makes a victim of the other; he making her over into what sounds like a parody of the beautifully turned-out woman ("a little clinging black jersey skirt, a red cashmere sleeveless shell . . . and on her feet a pair of pointy black slingbacks cut to show the cleavage of the foot"), she importing sex toys and women both real and imaginary into their bed and, thereby, eventually unmanning him.

What begins as a meditation on the source of artistic power and the artist's apparent helplessness to maintain it ends, then, as a lament for the loss of sexual power. This is clearly deliberate and not, in itself, completely spurious: few, surely, would argue that there is no connection between the two. But Roth's perplexing determination to vulgarise his narrative strips The Humbling of its own power: where he seeks to be nuanced, he too frequently appears trite; where he attempts to be brazen, he comes across as pointlessly crude. Sentences that are dismayingly free of Roth's characteristic humour and mischief pile up in a shakily fabular framework but never manage to animate the story's characters nor foreground its larger intentions. In spite of a final twist that delivers a much-needed emotional jolt, The Humbling falls into a trap that one cannot believe its author wished for it, nor that he hadn't the skill to avoid: it fails to give us enough to think about.